1. Field of the Invention
The invention described herein is directed to apparatuses and methods for aligning an optical fiber array housing optical fibers, with optical waveguides coupled to an optical integrated circuit (OIC) housed in an OIC assembly.
2. Description of the Related Art
Optical integrated circuits (OICs) are increasingly being used to implement optical devices including 1.times.N splitters, switches, wave division multiplexers (WDMs), and other optical devices, primarily due to the capability through optical device integration to obtain devices requiring relatively precise component configurations. Also, OICs generally have a more compact size and are more reliable and durable relative to discrein optical devices.
Often, an OIC is used in conjunction with optical fibers external to the OIC, that transmit optical signals to, and receive optical signals from, the OIC. Therefore, an interconnection needs to be established between the optical fibers and corresponding optical waveguides of the OIC. One technique used to couple optical fibers to optical waveguides of an OIC uses an OIC formed from silica (SiO.sub.2) with optical waveguides driven into the OIC using ion implantation (see "Reliability Studies of Single-Mode Optical Branching Devices", J. E. Matthews, III, et al., Corning Inc., November 1991). At an edge, the OIC has a step face extending from a top surface of the silica substrate transversely across the optical waveguides to a depth in the silica substrate. The OIC also has a ledge surface extending along a plane parallel to the top surface of the OIC that meets with the step face. In the step's face, cross-sections of the optical waveguides are exposed. An end of an optical fiber is aligned relative to a corresponding end of an OIC optical waveguide with micropositioners, and adhered to the corresponding OIC optical waveguide end exposed in the step's face. Also, at a distance away from the end of the optical fiber, the optical fiber is adhered to the ledge's surface. The alignment and adhesion of optical fibers ends to corresponding OIC optical waveguide ends and the ledge is repeated one-by-one until all desired optical fibers have been adhered to corresponding OIC waveguides. Although this technique is meritorious to an extent in that it allows for relatively good optimization of optical signal transmission from an optical fiber to an OIC's optical waveguide, the technique is relatively time-consuming and impractical for mass production because the optical fibers must be adhered one-by-one to the OIC's optical waveguides and the ledge. Further, the connection between optical fiber ends and respective ends of the OIC optical waveguides is relatively fragile and therefore can easily be broken. In addition, the connection between the optical fiber ends and respective OIC optical waveguides is not very durable, particularly in high humidity/temperature environments, because the adhesive loses bonding strength under these conditions which can cause the optical fiber ends to separate from the ends of the optical waveguides.
Another technique used to couple an OIC formed on a silica substrate to optical fibers uses silica-glass frames (see "Low-Loss and Stable Fiber-to-Waveguide Connection Utilizing UV Curable Adhesive", Y. Yamada, et al., I.E.E.E., 1992). Two optical fiber arrays are formed by sandwiching an array of optical fiber ends between respective silica and glass components which together define a frame. To aid in alignment of the fibers, the silica-glass frames include alignment grooves. Similarly, a silica substrate in which a 1.times.8 splitter is integrated, is sandwiched between silica and glass components which define a frame. A silica-glass frame housing an optical fiber array is positioned to oppose one end of the silica-glass frame housing the 1.times.8 splitter, and the other silica-glass frame housing the other optical fiber array is positioned to oppose the other end of the silica-glass frame housing the 1.times.8 splitter. The silica-glass frames are then positioned so that the optical fibers and the 1.times.8 splitter's optical waveguides are aligned, and the silica-glass frames are adhered together using an ultraviolet-curable adhesive. Although meritorious in some respects, this technique suffers from the significant disadvantage that glass and silica have different thermal coefficients of expansion so that the silica-glass frames, the optical fibers and the silica substrate in which the 1.times.8 splitter is formed, can develop internal stress or strain when subjected to certain temperatures, particularly temperatures different from those existing when the silica-glass frames are manufactured and assembled together. Therefore, the silica-glass frames, optical fibers and silica substrate can break or come apart under certain temperature conditions.